DE 37 00 447 A1 discloses a piece of furniture for sitting on, in which the body weight of a person is detected via the loading of a seat part and in which the leaning force required in order to adjust the inclination of the back part is to be adjusted as a function of the weight force of the person. This automatic adaptation takes place by a spring being compressed by the weight force of the person, with the backrest carrier acting against this compressed spring. A disadvantage of a piece of furniture of this type for sitting on is that, here, only the weight force acting on the seat part can be detected. A weight force introduced via the back part or armrests which may be present cannot be correctly detected by the mechanism, since it is dissipated via the coupling of the carrier of the back part also to the seat carrier. This may possibly result in too weak a reaction force of the carrier of the back part.
Furthermore, U.S. Pat. No. 5,080,318 discloses a control device for the inclination of a chair comprising a weighing device which causes an adjustment of a tension device for a leaf spring which cushions an inclination of the seat, the adjustment travel being dependent on the weight of a user. A control device of this type has the disadvantage that the weighing of a user and therefore the setting of the leaf spring take place under load and are therefore sluggish and consequently slow and inaccurate.